Background: Myelodysplastic syndromes (MDSs) include a diverse group of clonal bone marrow disorders characterized by ineffective hematopoiesis and pancytopenia.It was found that down regulation of APAF1, a putative tumor suppressor gene (TSG),leads to resistance to chemotherapy and disease development in some cancers. In this study, we investigated the relation of APAF1 methylation status with its expression and clinicopathological factors in myelodysplastic syndrome (MDS) patients. Materials and Methods: Methylation Sensitive-High Resolution Melting Curve Analysis (MS-HRM) was employed in studying the methylation of CpG islands in the APAF1promoter region in MDS. Gene expression was analyzed by using real time RT-PCR. Results: 42.6% of patient samples were methylated in promoter region of APAF1 analyzed, while methylation of the genewas not seen in controls (P